The patch titled
Subject: x86/mmap: properly account for stack randomization in mmap_base
has been added to the -mm tree. Its filename is
x86-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/x86-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/x86-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
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------------------------------------------------------
From: Rik van Riel <riel@xxxxxxxxxx>
Subject: x86/mmap: properly account for stack randomization in mmap_base
When RLIMIT_STACK is, for example, 256MB, the current code results in a
gap between the top of the task and mmap_base of 256MB, failing to take
into account the amount by which the stack address was randomized. In
other words, the stack gets less than RLIMIT_STACK space.
Ensure that the gap between the stack and mmap_base always takes stack
randomization and the stack guard gap into account.
Obtained from Daniel Micay's linux-hardened tree.
Link: http://lkml.kernel.org/r/20170622200033.25714-2-riel@xxxxxxxxxx
Signed-off-by: Daniel Micay <danielmicay@xxxxxxxxx>
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Reported-by: Florian Weimer <fweimer@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Daniel Micay <danielmicay@xxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/mmap.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN arch/x86/mm/mmap.c~x86-mmap-properly-account-for-stack-randomization-in-mmap_base arch/x86/mm/mmap.c
--- a/arch/x86/mm/mmap.c~x86-mmap-properly-account-for-stack-randomization-in-mmap_base
+++ a/arch/x86/mm/mmap.c
@@ -95,13 +95,18 @@ unsigned long arch_mmap_rnd(void)
static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)
{
unsigned long gap = rlimit(RLIMIT_STACK);
+ unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
unsigned long gap_min, gap_max;
+ /* Values close to RLIM_INFINITY can overflow. */
+ if (gap + pad > gap)
+ gap += pad;
+
/*
* Top of mmap area (just below the process stack).
* Leave an at least ~128 MB hole with possible stack randomization.
*/
- gap_min = SIZE_128M + stack_maxrandom_size(task_size);
+ gap_min = SIZE_128M;
gap_max = (task_size / 6) * 5;
if (gap < gap_min)
_
Patches currently in -mm which might be from riel@xxxxxxxxxx are
randomstackprotect-introduce-get_random_canary-function.patch
forkrandom-use-get_random_canary-to-set-tsk-stack_canary.patch
x86-ascii-armor-the-x86_64-boot-init-stack-canary.patch
arm64-ascii-armor-the-arm64-boot-init-stack-canary.patch
sh64-ascii-armor-the-sh64-boot-init-stack-canary.patch
x86-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
arm64-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
powerpcmmap-properly-account-for-stack-randomization-in-mmap_base.patch
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